One of the enigmas in studying cognitive activities is that it is difficult to separate the relative motivational effort expended by a subject in performing a task from the effectiveness of processing operations. It has long been suggested that such information is accessible through pupillary assessment. The objective of this revised application is to investigate the extent to which differential sympathetic and parasympathetic innervation of the pupillary response is associated with different cognitive processes in normal human subjects. We hypothesize that separate components can be identified that reflect sympathetic and parasympathetic contributions to pupillary activity. These components can be employed to distinguish effort involved during task performance from effectiveness of information utilization. Hypotheses to be tested are: (a) Cognitive evaluation of information (stimulus salience) is related to direct sympathetic activation that is mediated by posterior hypothalamic integrating centers. (b) In contrast, motivation to perform, the utilization of effort, and motor activity are related to inhibition of the central parasympathetic pathway. (c) During cognitive activity, the pupillary pathways are innervated primarily by endogenous processes. Thus, pupillary activity should be similar when information is either provided by a specific stimulus or emitted following the absence of a stimulus at a critical point in time. Comparison of recordings obtained under dark vs. light- adapted conditions can be used to accentuate the autonomic components. In darkness, sympathetically mediated activity will be most prominent. Conversely, under light adaption, parasympathetically mediated activity will be highlighted. More precise isolation of central pathways will be evaluated by selective-pharmacological blockade of pupillary muscles. During blockade of the sphincter, dilation which is mediated by sympathetic stimulation will be isolated. Conversely, during blockade of the dilator, dilation which is mediated by parasympathetic inhibition will be isolated. This proposal provides the first empirical tests for these hypotheses. The findings of this study will provide objective criteria that reflect the activity of specific central physiological pathways. These criteria can be employed to distinguish information processing operations from motivational effort to perform. Ultimately, the findings can be applied to questions regarding attention and processing integrity, with particular application to neuropsychiatric disorders.